Adjustable cam



J. L. KING ADJUSTABLE CAM April 14, 1964 Filed Aug. 15, 1961 INVENTOR.

JAMES L. KING ATTORNEYS United States Patent 3,128,638 ADJUSTABLE CAMJames .L. .K-ing, Sudbury, Mass, .assignor to Acton Lahoratories,lne.,a. corporation of Massachusetts Filed Aug. 15, 19.61, Ser. No. 131,579-7' Claims. '(Cl. 7.4-568) Thisinvention relates: to timing cams andmore particularly to ,a new and improved adjustable timing camassembly'for use in actuating electrical switches at precise timeintervals.

The primary object of the present invention is to ,provide a new andimproved timing cam for an electric switch which permits precisionadjustment of the time -at which the switch is actuated.

Afurther primary object of'the present invention is to provideanadjustable timing cam for an electric switch which permitsprecisionvariation of the-length of time ;during which the switch is.held operative or inoperative by the cam.

:,Still another'primary object of the present invention is .to providean-adjustable timing cam which will not shift ifrom its setposition-under vibration and'yet may be reset easily by a simpleconventional tool.

.Amorespecific object of the present invention is to provide a timingcam assembly which-comprises a first ihlll) unit adapted to beadjustably' mounted'on a rotating shaft, and a second cam memberretainedby thehub .unitandselec'tively rotatable relative to the hub unit and.the shaft, the cam member being rotatable by means of .a worm which isrotatably'captivated within the'hub 'unit .in a manner such that it issubstantially-free of axial movement.

Still a further objectof the present invention is to provide .a camassembly-as described in the foregoing statement of object, whichfurther includes a second cam'member .supportedbythe first cam memberand rotatable rela- -tive to the hub-unit and the first cam memberby-aseccation when considered together with theaccompanying "drawingswherein:

FIG. '1 is a perspective view of a cam assembly embodying-the presentinvention mounted -on a supporting rotatable shaft;

FIG. 2 is a perspective view of the same cam assembly and supportingshafttaken'fromanothertvantage point;

FIG. 3 is a longitudinalsectional view of the structure shown inFIGURES'l and 2;

FIG; 4 isa-cross-sectionai-View taken along line'44 of FIG. 3; and

FIG. 5 is an cxplodedvviewshowing the various components of the camassembly.

The illustrated cam assembly comprises a hub unit which is made up of ahub member 2 and a surrounding sleeve 4. The hub member 2 is providedwith a central bore to accommodate a supporting shaft 6 which is drivenby motor means (not shown). The central bore of hub member 2 is enlargedas shown at 8 so as to accommodate one of the hubs 10 of a dual-hub cammember 12 having a central bore 14. The opposite hub portion of cammember 12 is illustrated at 16. Hub portion 10 is provided with aperipheral, helically threaded groove 18 sized to accept and mesh with aworm 20 which is captivated within bore 22 formed in the hub member 2.Preferably, worm 20 has an Allen type head as shown, but it may alsohave a kerfed head. It is to be noted that the bore 22' partiallyintersects the enlarged portion 3,128,638 Patented Apr. 14,1964

8 of the central bore of hub member 2 and .also that it is reduced indiameter as indicated at 24 so as to form a shoulder 26 againstwhichthehead of the worm can abut. Axial movement of the screw away fromshoulder .26 is prevented by a plug 30 of a suitable plastic, or ametallic cement which is forced into the open end of bore 22. Plug 30 isretained in place by the surrounding sleeve 4 which is force fittedontohub member 2. In this connection it is to be observed that thesleeve 4 has a hole 34 which is aligned with the restricted section 24of the bore 22, so as to permit insertion of van Allen wrench or ascrewdriver, asthe case may be, forrotating the worm. It is to beobserved further that hub memberlZ' and its companionsleeve 4 areprovided .with matching radial bores 36 and 38,to accommodate a setscrew 40. .The latter is used to secure the hub unit to shaftf6.

The peripheral edge of cam member 12 is provided with-acamconfiguration. In the. present-case it is circular except for adepression 44. Alternatively, it may be ellipticalor have aseries ofdepressions orv projections,

depending uponthe requirements to be satisfied. The edges of the cammember may be varied in-width to the extent necessary to assure goodcontact with the actuatfling memberof the switch. In most cases theswitch actuating member will bea button ora spring-biased lever.Preferably the cam element 12 is formed of nylon or some otherstrong,,hard.wearing, easilymachinable material which can be rotatedrelative adjacent members without any substantial friction.

Rotation of worm 20.will cause cam member 12 to rotate relative to theshaft 6. In this connection, it is to be observed that the center bore14 .of cam. member 12 is slightly; larger than shaft 6rso as .to permitthe cam to rotate freely on the shaft. Atthe same time, however,

the spacing between the bore, 14 and theshaft ,6 is sufiiciently smallas to permit the shaft to provide support for the cam element.

Also supported by the cam element 12 is a second cam member 48 havinganedge depressiont50. Cam member 48 has a hub 52 and a center hole 54which is sized to accept hub16 ofcammember 12. I-Iub16 hasa peripheral,helically threaded .groove .56 which. is the-same as groove 18. Groove56 accepts a second worm 58 which .ispositioned in a bore60 formed in.cam member. 48. Al-

though not shown in detail, it is .to. be understood that bore 60 is thesame asbore 22 andworm58is captivated .by a plug the same as plug30.Surrounding hub 52 of primary function is to retainplug 3t) and itscounterpart'for worm58 so to prevent axial movement of worms 20 and.5;8.

It is believed to be apparent that. rotation of. worm .53

will causecam member 48 to rotate relative tocam member 12in the sameway that cam member 12 will rotate relative to hub member 2 and shaft 6when worm 20 is turned. When depressions 44 and 50 are exactly in line,the two cam members will function as if only one of them were present.However, if one cam member is rotated slightly so that depressions 44and 50 partially overlap, the dwell time will be changed according tothe amount of overlap. In addition to permitting adjustment of thelength of dwell time, the foregoing construction permits adjustment ofthe start of the dwell period by rotation of cam member 2. In otherwords, actuation of the switch associated with the cam assembly can beadvanced or retarded by turning worm 20 and the duration of the periodof actuation can be increased or decreased by turning worm 58.

A further advantage of the invention is that the second cam member 48may be omitted without aifecting the function or design of cam member12. However, if cam member 48 is omitted, it may be desirable toeliminate hub 16 of cam member 12'.

It is to be noted also that although cam members 12 and 48 areconstructed so as to lie against one another so as to function as asingle adjustable cam, it is possible also to form either cam member sothat their edges are spaced axially a sufficient distance to function astwo separate cams separately adjustable relative to shaft 6.

A most significant feature of the invention is the simplified manner ofmounting the worms 20 and 58. Forming the bores 22 and 60 and theirrestricted extensions is easily accomplished using conventional tools.Also a simple matter is insertion of the plugs 30 and press-fitting ofsleeves 4 and 62. Use of the sleeves assures that the plugs will notcome out or shift under vibration, heat, or pressure. The plugs can bemade to exert an axial force on the worms which not only prevents themfrom moving axially but also helps restrain them against rotation.Hence, the cam members will be held firm in their set positions and willnot shift or chatter under vibration or sudden shock. Lack of chatter onthe part of the cam members is important where precision timing isrequired, as, for example, in airborne telemetry and control systems.

Another feature of the invention is ease of assembly due to the factthat cam member 12 is made of a resilient plastic such as nylon. Cammember 12 is snapped into place in hub member 2, the former compressingsufficiently so as to snap over worm 20. Cam member 48 also is snappedover hub 16 of cam member 12. In the latter case hub 16 yieldssufliciently to allow worm 58 to be snapped into groove 56. Onceassembled, the members cannot be separated except by deliberately pryingthem apart with a sharp tool.

Obviously, many modifications and variations of the present inventionare possible in the light of the foregoing teachings. It is to beunderstood, therefore, that the invention is not limited in itsapplication to the details of construction and arrangement of partsspecifically described or illustrated, and that within the scope of theappended claims it may be practiced otherwise than as specificallydescribed or illustrated.

What is claimed is:

1. A timing cam assembly comprising a hub member, means for securingsaid hub member to a rotatable shaft, a first cam member rotatablysupported by said hub member, means for controllably rotating andlocking said first cam member relative to said hub member, a second cammember rotatably mounted on said first cam member, and means forcontrollably rotating and locking said second cam member relative tosaid first cam member.

2. A timing cam assembly as defined by claim 1 wherein said means forrotating and locking said first cam member comprises a helical gear onsaid first cam member and a worm carried by said hub member which mesheswith said gear.

3. A timing cam assembly as defined by claim 1 wherein said means forrotating and locking said second cam member comprises a second helicalgear on said first snugly within said first section, a transverselyextending bore in said hub member, a worm rotatably disposed in saidtransversely extending bore, a sleeve surrounding said hub member forpreventing axial movement of said worm, and a cam member having a hubdisposed within said second section of said axial bore, said hub havinga peripheral groove with a helical thread formed therein, said wormpositioned in said groove in meshing engagement with said helicalthread, whereby as said worm is rotated said cam member will rotateabout its center axis relative to said hub member.

6. A timing cam assembly comprising a hub member having an axial bore,said axial bore having a first section of relatively small diameter forsnugly receiving a shaft and a second section of relatively largediameter, means for securing said hub member to a shaft fitting snuglywithin said first section, a first transversely extending bore in saidhub member, a first worm rotatably disposed in said first transverselyextending bore, means preventing axial movement of said first Worm, afirst cam member having a first hub disposed within said second sectionof said axial bore, a said first hub having a first peripheral groovewith a helical thread formed therein, said first worm positioned in saidfirst groove in meshing engagement with the helical thread therein,whereby as said first worm is rotated said first cam member will rotateabout its center axis relative to said hub member, a second hub on saidfirst cam member having a second peripheral groove with a helical threadformed therein, a second cam member rotatably mounted on said secondhub, said second cam member having a second transverse- .ly extendingbore, a second worm rotatably disposed in said second bore in meshingengagement with the helical thread in said second helical groove, andmeans preventing axial movement of said second worm, whereby as saidsecond worm is rotated said second cam member ,will rotate relative tosaid first cam member.

7. A timing cam assembly as defined by claim 6 wherein said second cammember has a hub portion with said second worm located therein, and saidmeans for preventing axial movement of said second worm comprises asleeve surrounding said hub portion.

References Cited in the file of this patent UNITED STATES PATENTS2,857,784 Brailsford Oct. 28, 1958 FOREIGN PATENTS 3,659 NetherlandsSept. 5, 1919

1. A TIMING CAM ASSEMBLY COMPRISING A HUB MEMBER, MEANS FOR SECURINGSAID HUB MEMBER TO A ROTATABLE SHAFT, A FIRST CAM MEMBER ROTATABLYSUPPORTED BY SAID HUB MEMBER, MEANS FOR CONTROLLABLY ROTATING ANDLOCKING SAID FIRST CAM MEMBER RELATIVE TO SAID HUB MEMBER, A SECOND CAMMEMBER ROTATABLY MOUNTED ON SAID FIRST CAM MEMBER, AND MEANS FORCONTROLLABLY ROTATING AND LOCKING SAID SECOND CAM MEMBER RELATIVE TOSAID FIRST CAM MEMBER.